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I recently installed 8GB of RAM onto a quad core workstation (HP xw8600) running Windows XP Pro (32-bit). I added the /PAE switch in the boot.ini file, but the SysInfo is saying 3GB total memory still. Is Windows recognizing the extra memory? Is there a way to tell?

Any help is appreciated. Thanks.

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it's NOT about XP, it's about it being 32 bit ... 64 bit will support all your 8GB and then some

(Windows XP Professional x64 Edition supports 128 GB of RAM)[http://www.microsoft.com/windowsxp/using/64bit/russel_exploringx64.mspx]

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    not entirely true. PAE allows 32-bit OSs to access up to 64GB of RAM. The real issue is that MS deliberately doesn't use RAM found above the 4GB mark on 32-bit system due to common errors in 3rd party drivers. see blog.codef00.com/2007/12/19/windows-on-x86-and-4gb-of-ram – Evan Teran Apr 2 '09 at 21:17
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    In addition, my linux box (which is using a 32-bit kernel) currently happily uses 8GB of RAM through the use of PAE (the option is called enabled 64GB ram, but it basically means "turn on pae support" – Evan Teran Apr 2 '09 at 21:18
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from http://www.microsoft.com/whdc/system/platform/server/PAE/PAEmem.mspx

"Windows XP Professional and Windows Server 2003 Memory Support. The maximum amount of memory that can be supported on Windows XP Professional and Windows Server 2003 is also 4 GB. However, Windows Server 2003, Enterprise Edition supports 32 GB of physical RAM and Windows Server 2003, Datacenter Edition supports 64 GB of physical RAM using the PAE feature."

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    Why does the MS article say 4GB but everyone else is saying 3.x GB. It is confusing. – johnny Apr 2 '09 at 21:20
  • Finally someone gives a fully accurate answer! – Evan Teran Apr 2 '09 at 21:23
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    @jhonny: it is because that is 4GB minus any memory mapped devices ram (such as your video card). If you have a 512 meg video card, windows only acknowledges 3.5 of RAM (devices have to be mapped below 4GB for 32-bit DMA to work right). – Evan Teran Apr 2 '09 at 21:24
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XP will only recognize up to 3.5GB. So no, XP will not reognize the extra memory.

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    XP 64-bit - WILL – roman m Apr 2 '09 at 20:34
  • THat's not exactly true. See my post below. – Foredecker Apr 2 '09 at 20:34
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This is totally off topic, but 32-bit Windows can't use more than 4 GB - desktop versions of Windows 32-bit will only give you about 3.5GB. (This limit is in place because buggy drivers often assume the top of the memory address space is not used and will crash your machine if you actually use up to 4GB. Servers are assumed to have better drivers.)

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    not true, if the OS supports PAE properly, it can use up to 64GB of RAM. Linux has been doing this for years. – Evan Teran Apr 2 '09 at 21:21
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32-bit operating systems max out around 3 gigs.

In order to take advantage of that much ram, you need a 64-bit os.

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    change that to "32-bit windows" and it's true. If the OS supports PAE properly, it can use up to 64GB of RAM. Linux has been doing this for years. – Evan Teran Apr 2 '09 at 21:22
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The short answer is no.

You can find the long answer here: http://blogs.technet.com/markrussinovich/archive/2008/07/21/3092070.aspx

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Switch to 64bit and you'll see the whole 8 GB.

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You can't have more than 3.5 GB on Windows XP Pro 32 bit edition.

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Here is a more detailed explanation, it's not about Windows, it's an x86 thing: http://www.codinghorror.com/blog/archives/000811.html

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It seems like you're not allowed to use the PAE at all on a 'normal (non server)' 32-Bit Windows, maybe this does help (yes, I know it's for Vista...).

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  • there's this. – user2284570 Apr 4 '14 at 20:28
  • @user2284570 As far as I know, enabling PAE on a home system is a license violation. – Bobby Apr 5 '14 at 9:20
  • Yes and not only for home... For every non-server 32-bit windows version since XP SP2 (yes xp SP1 and windows 2000 support >4GB by manually adding the /PAE switch to boot.ini). – user2284570 Apr 5 '14 at 15:23